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Type 2 diabetes is characterized by impairment in insulin secretion, with an established genetic contribution. We aimed to evaluate common and low-frequency (1-5%) variants in nine genes strongly associated with insulin secretion by targeted sequencing in subjects selected from the extremes of insulin release measured by the disposition index. Collapsing data by gene and/or function, the association between disposition index and nonsense variants were significant, also after adjustment for confounding factors (OR = 0.25, 95% CI = 0.11-0.59, p = 0.001). Evaluating variants individually, three novel variants in ARAP1, IGF2BP2 and GCK , out of eight reaching significance singularly, remained associated after adjustment. Constructing a genetic risk model combining the effects of the three variants, only carriers of the ARAP1 and IGF2BP2 variants were significantly associated with a reduced probability to be in the lower, worst, extreme of insulin secretion (OR = 0.223, 95% CI = 0.105-0.473, p < 0.001). Observing a high number of normal glucose tolerance between carriers, a regression posthoc analysis was performed. Carriers of genetic risk model variants had higher probability to be normoglycemic, also after adjustment (OR = 2.411, 95% CI = 1.136-5.116, p = 0.022). Thus, in our southern European cohort, nonsense variants in all nine candidate genes showed association with better insulin secretion adjusted for insulin resistance, and we established the role of ARAP1 and IGF2BP2 in modulating insulin secretion.

Introduction: Dipeptidyl peptidase 4 (DPP4) levels are associated to metabolic and cardiovascular diseases in humans; initial evidence reported a relationship between DPP4 and chronic liver diseases. Aim of this study was to investigate hepatic and systemic DPP4 levels/activity in relation to NAFLD/NASH in individuals with and without metabolic disease., Methods: We recruited fifty-two obese individuals undergoing bariatric surgery and intra-operative liver biopsy at Sapienza University, Rome, Italy. The association between DPP4 levels/activity and NAFLD was also evaluated in 126 non-obese individuals recruited in the same setting., Results: NAFLD patients had significantly higher circulating DPP4 activity than no-NAFLD in both the obese and non-obese cohorts; plasma DPP4 activity and levels linearly correlated with steatosis grade and inflammation at the liver biopsy. Hepatic DPP4 mRNA was not associated to either its circulating levels/activity or NAFLD. In the multivariate logistic regression analysis on all the study participants (n = 178), higher circulating DPP4 activity was associated with NAFLD independently of potential confounders with OR (95% CI): 3.5 (1.2-10.21), p = 0.022., Conclusions: This study demonstrates the coexistence of increased plasma DPP4 levels and activity in NAFLD. Circulating DPP4 measurement may represent a novel cost-effective strategy for NAFLD/NASH risk stratification and a potential tool for monitoring disease's progression in established NAFLD.

Aims: Experimental data suggest that visceral adipose tissue (VAT) dysfunction contributes to non-alcoholic fatty liver disease (NAFLD) development in obesity, however, data on humans are limited. Aims of this study were to investigate the relationship between NAFLD and VAT morphofunctional impairment and to determine whether the extent of VAT remodelling is associated with liver damage and metabolic alterations in obesity., Methods: We analysed data from 40 obese individuals candidate to bariatric surgery in whom paired intraoperative liver and omental biopsies were performed for diagnosing NAFLD and VAT inflammation by immunohistochemistry and mRNA expression studies., Results: Within our study population, NAFLD was significantly associated with greater VAT CD68 + macrophages infiltration (P = .04), fibrosis (P = .04) and impaired microvascular density (P = .03) as well as increased expression of markers of local hypoxia, apoptosis and inflammation (UNC5B, CASP7, HIF1-α, IL-8, MIP2, WISP-1, all P < .01). The degree of VAT inflammation correlated with the severity of hepatic injury (steatosis, inflammation, fibrosis; all P < .01) and impaired gluco-metabolic profile., Conclusions: In obese patients, NAFLD is associated in a dose-dependent manner with signs of VAT remodelling, which reflect more severe clinical metabolic impairment. Our study depicts morphological alterations and novel mediators of VAT dysfunction, adding knowledge for future therapeutic approaches to NAFLD and its metabolic complications., (© 2020 John Wiley & Sons Ltd.)

Biliverdin reductase A (BVR-A) is an enzyme involved in the regulation of insulin signalling. Knockout (KO) mice for hepatic BVR-A, on a high-fat diet, develop more severe glucose impairment and hepato-steatosis than the wild type, whereas loss of adipocyte BVR-A is associated with increased visceral adipose tissue (VAT) inflammation and adipocyte size. However, BVR-A expression in human VAT has not been investigated. We evaluated BVR-A mRNA expression levels by real-time PCR in the intra-operative omental biopsy of 38 obese subjects and investigated the association with metabolic impairment, VAT dysfunction, and biopsy-proven non-alcoholic fatty liver disease (NAFLD). Individuals with lower VAT BVR-A mRNA levels had significantly greater VAT IL-8 and Caspase 3 expression than those with higher BVR-A. Lower VAT BVR-A mRNA levels were associated with an increased adipocytes' size. An association between lower VAT BVR-A expression and higher plasma gamma-glutamyl transpeptidase was also observed. Reduced VAT BVR-A was associated with NAFLD with an odds ratio of 1.38 (95% confidence interval: 1.02-1.9; χ 2 test) and with AUROC = 0.89 ( p = 0.002, 95% CI = 0.76-1.0). In conclusion, reduced BVR-A expression in omental adipose tissue is associated with VAT dysfunction and NAFLD, suggesting a possible involvement of BVR-A in the regulation of VAT homeostasis in presence of obesity.

Granzyme B (GrB) is a serine protease produced by immune and non-immune cells, able to promote multiple processes, like apoptosis, inflammation, extracellular matrix remodeling and fibrosis. GrB expression in visceral adipose tissue (VAT) was associated with tissue damage, local inflammation and insulin resistance in obesity murine model, but there is no data in humans. Aim of this study was to explore the expression of GrB in VAT from obese subjects in relation to adipose tissue injury, inflammation, metabolic alterations and GrB circulating levels. For this purpose, 85 obese individuals undergoing bariatric surgery and 35 healthy subjects (as control) were recruited at Sapienza University, Rome, Italy. Study participants underwent clinical work-up and routine biochemistry. mRNA expression of GrB in VAT and of a panel of VAT inflammatory markers was analyzed by real-time PCR. Serum GrB levels were measured by Elisa Affymetrix EBIO. We observed that 80% of obese patients expressed GrB mRNA in VAT, and GrB VAT expression was associated with the presence of local inflammation and glucose homeostasis alterations. Moreover, GrB serum levels, which were higher in obese subjects compared to non-obese healthy individuals, were associated with GrB expression in VAT and glyco-metabolic impairment. Our data show, for the first time in humans, that obese subjects with "sick" fat and altered glucose tolerance exhibit GrB expression in VAT, and suggest that GrB might contribute to obesity-related VAT inflammatory remodeling and glucose homeostasis dysregulation. Moreover, increased circulating GrB levels might represent a possible peripheral marker of VAT dysfunction in metabolic diseases., (Copyright © 2020 Cimini, Barchetta, Ceccarelli, Chiappetta, Di Biasio, Bertoccini, Sentinelli, Leonetti, Silecchia, Di Cristofano, Baroni, Velotti and Cavallo.)

Angiopoietin-like protein 4 (ANGPTL4) regulates lipid partitioning by inhibiting circulating and tissue lipoprotein lipase (LPL); ANGPTL4 loss-of-function variants improve insulin sensitivity and reduce type 2 diabetes (T2D) risk with mechanisms partially unknown. This study was designed to explore metabolic implications of differential ANGPTL4 and LPL expression in human adipose tissue (AT). We recruited eighty-eight obese individuals, with and without abnormal glucose metabolism (AGM), undergoing bariatric surgery; visceral AT (VAT) fragments were obtained intra-operatively and analyzed by immunohistochemistry and mRNA by rt-PCR. Data on hepatic ANGPTL4 mRNA were available for 40 participants. VAT ANGPTL4 expression was higher in AGM individuals than in those with normal glucose tolerance (NGT) and associated with VAT inflammation, insulin resistance, and presence of adipocyte size heterogeneity. Increased ANGPTL4 was associated with AGM with OR = 5.1 (95% C.I.: 1.2-23; p = 0.02) and AUROC = 0.76 (95% C.I.: 1.2-23; p < 0.001). High LPL was associated with the detection of homogeneous adipocyte size, reduced microvessel density, and higher HIF-1α levels and inversely correlated to blood transaminases. In conclusion, in obese individuals, VAT ANGPTL4 levels are increased in the presence of local inflammation and AGM. Conversely, higher LPL expression describes a condition of increased lipid storage in adipocytes, which may serve as a protective mechanism against ectopic fat accumulation and related metabolic disease in obesity.

Biliverdin reductase-A (BVR-A) is a serine/threonine/tyrosine kinase involved in the regulation of insulin signaling. In vitro studies have demonstrated that BVR-A is a substrate of the insulin receptor and regulates IRS1 by avoiding its aberrant activation, and in animal model of obesity the loss of hepatic BVR-A has been associated with glucose/insulin alterations and fatty liver disease. However, no studies exist in humans. Here, we evaluated BVR-A expression levels and activation in peripheral blood mononuclear cells (PBMC) from obese subjects and matched lean controls and we investigated the related molecular alterations of the insulin along with clinical correlates. We showed that BVR-A levels are significantly reduced in obese subjects and associated with a hyper-activation of the IR/IRS1/Akt/GSK-3β/AS160/GLUT4 pathway. Low BVR-A levels also associate with the presence of obesity, metabolic syndrome, NASH and visceral adipose tissue inflammation. These data suggest that the reduction of BVR-A may be responsible for early alterations of the insulin signaling pathway in obesity and in this context may represent a novel molecular target to be investigated for the comprehension of the process of insulin resistance development in obesity., (Copyright © 2019 Elsevier B.V. All rights reserved.)

Introduction: Copeptin is the stable surrogate marker of vasopressin (VP), which is released in response to elevated plasma osmolality or low blood pressure. Elevated plasma copeptin levels are associated with higher risk of insulin resistance-related disorders, such as type 2 diabetes (T2DM), metabolic syndrome (MS), and cardiovascular disease, and experimental reduction of circulating VP levels is shown to significantly decrease hepatic fat content in obese rats, independently from body adiposity. However, the association between copeptin and non-alcoholic fatty liver disease and steatohepatitis (NAFLD/NASH) in humans has not been explored yet. The aim of this study was to explore the relationship between plasma copeptin and the presence/severity of NAFLD/NASH., Methods: For this study, we recruited 60 obese patients candidate to bariatric surgery for clinical purposes in which intraoperative liver biopsies were performed for diagnosing NAFLD/NASH. Circulating copeptin levels were also assessed in 60 age- and sex-comparable non-obese individuals without NAFLD at liver ultrasonography. Plasma copeptin was measured by sandwich immunoluminometric assay (Thermo Fisher Scientific)., Results: Obese patients with biopsy-proven NAFLD (53%) had significantly higher copeptin levels than both obese individuals without NAFLD and non-obese subjects (ob/NAFLD+ 9.5 ± 4.9; ob/NAFLD- 6.4 ± 2.6; and non-ob/NAFLD- 7.4 ± 5.1 pmol/L; p = 0.004 and p = 0.01 respectively). Plasma copeptin concentration positively correlated with hepatic macro- and micro-vesicular steatosis (r = 0.36, p = 0.026; r = 0.31, p = 0.05), lobular inflammation (r = 0.37, p = 0.024) and significantly increased throughout degrees of NASH severity, as expressed as absence, borderline, and overt NASH at the liver biopsy (r = 0.35, p = 0.01). Greater circulating copeptin predicted the presence of NASH with OR = 1.73 (95% CI = 1.02-2.93) after multivariate adjustment for age, sex, renal function and presence of T2DM and MS components., Conclusions: Increased plasma copeptin is independently associated with the presence and severity of NAFLD and NASH, pointing to a novel mechanism behind human fatty liver disease potentially modifiable by pharmacological treatment and lifestyle intervention.

Context: Neurotensin (NT), an intestinal peptide released by fat ingestion, promotes lipid absorption; higher circulating NT levels are associated with type 2 diabetes (T2D), obesity, and cardiovascular disease. Whether NT is related to nonalcoholic fatty liver disease (NAFLD) and nonalcoholic steatohepatitis (NASH) has not been fully investigated., Objective: To study the relationship between plasma proneurotensin 1 to 117 (pro-NT), a stable fragment of the NT precursor hormone, and the presence/severity of NAFLD/NASH and to unravel correlates of increased pro-NT levels., Design/setting/participants: For this cross-sectional study, 60 obese individuals undergoing bariatric surgery for clinical purposes were recruited. The association between pro-NT and NAFLD was further investigated in 260 consecutive subjects referred to our outpatient clinics for metabolic evaluations, including liver ultrasonography. The study population underwent complete metabolic characterization; in the obese cohort, liver biopsies were performed during surgery., Main Outcome Measures: Plasma pro-NT levels in relation to NAFLD/NASH., Results: Obese subjects with biopsy-proven NAFLD (53%) had significantly higher plasma pro-NT than those without NAFLD (183.6 ± 81.4 vs 86.7 ± 56.8 pmol/L, P < 0.001). Greater pro-NT correlated with NAFLD presence (P < 0.001) and severity (P < 0.001), age, female sex, insulin resistance, and T2D. Higher pro-NT predicted NAFLD with an area under receiver operating characteristic curve of 0.836 [95% confidence interval (CI), 0.73 to 0.94; P < 0.001]. Belonging to the highest pro-NT quartile correlated with increased NAFLD risk (odds ratio, 2.62; 95% CI, 1.08 to 6.40) after adjustment for confounders. The association between higher pro-NT and NAFLD was confirmed in the second cohort independently from confounders., Conclusions: Increased plasma pro-NT levels identify the presence/severity of NAFLD; in dysmetabolic individuals, NT may specifically promote hepatic fat accumulation through mechanisms likely related to increased insulin resistance.

Background: Apolipoprotein A-V (ApoA-V) is a recognized regulator of plasma triglycerides (TGs), and previous studies have shown associations between variants in APOA5 (apolipoprotein-A5) gene and high TG levels. Recently, a new association between the Arg282Ser missense mutation (rs778114184 G > T) in APOA5 gene and decreased triglyceride levels has been shown in an adult population from Sardinia. In this study we add further insight into the role of APOA5 by exploring whether this association begins early in life in children, or becomes manifest only in adulthood. We performed the genetic association analysis of APOA5 in a cohort of 925 overweight and obese children and adolescents from Sardinia, Italy, to see if the genetic burden is already at play before modifying risk factors are interacting., Results: We identified 24 heterozygous subjects for the Arg282Ser variant and no homozygous subject. Here we show that the Arg282Ser mutation in APOA5 gene is associated with a significant reduction of TG (-15.5 mg/dl), total (-18.1 mg/dl) and LDL-cholesterol (-14.8 mg/dl) levels in overweight/obese children and adolescents, indicating that indeed this association appears early in life. Also, we observed a significant reduction in serum apoA-V levels in heterozygous children., Conclusions: Our data clearly show that the Arg282Ser mutation in APOA5 gene determines a reduction of TG, total and LDL-cholesterol and apolipoprotein A-V levels in overweight/obese children and adolescents, demonstrating that this mutation has the power to affect lipid levels already since childhood.

Background: Metabolic syndrome (MS) and hypovitaminosis D represent two of the most diffuse condition worldwide, reaching pandemic proportions in industrialized countries, and are both strongly associated with obesity. This study set out to evaluate the presence of an independent association between hypovitaminosis D and MS in an adult population of obese subjects with/without MS., Methods: We recruited 107 consecutive obese subjects, 61 with MS (age(mean±SD) 45.3±13.3 years, BMI(mean±SD): 43.1±8.3 kg/m(2)) and 46 without MS (age: 41.8±11.5, p = n.s., BMI:41.6±6.5 kg/m(2), p = n.s.) comparable for sex, BMI, waist circumference and body fat mass, evaluated by bioimpedentiometry. 25(OH) vitamin D3 levels were measured by colorimetric method. Insulin resistance was estimated by fasting blood insulin, HOMA-IR and ISI., Results: Serum 25(OH)D3 levels were significantly lower in MS obese patients than in obese subjects without MS (median(range) 13.5(3.3-32) vs 17.4(5.1-37.4), p<0.007). Low 25(OH)D3 levels correlated with glycaemia (p<0.007), phosphate (p<0.03), PTH (p<0.003) and the MS (p<0.001). Multivariate model confirmed that low 25(OH)D3 levels were associated with the diagnosis of MS in obese patients independently from gender, age, serum PTH and body fat mass. After stratifying the study population according to 25(OH)D3 concentrations, patients in the lowest quartile showed a markedly increased prevalence of MS compared to those in the highest quartile (OR = 4.1, CI 1.2-13.7, p = 0.02)., Conclusions: A powerful association exists between hypovitaminosis D and MS in obese patients independently from body fat mass and its clinical correlates. This indicates that the association between low 25(OH) D3 levels and MS is not merely induced by vitamin D deposition in fat tissue and reinforces the hypothesis that hypovitaminosis D represent a crucial independent determinant of MS.

Obesity is recognized as a major health problem worldwide. Genetic factors play a major role in obesity, and genomewide association studies have provided evidence that several common variants within the fat mass- and obesity-associated (FTO) gene are significantly associated with obesity. Very limited data is available on FTO in the Italian population. Aims of our study are to investigate: (1) the association of FTO gene SNPs rs9939609 and rs9930506 with body mass index (BMI) and obesity-related parameters in a large cohort (n = 752) of Italian obese subjects; (2) the association between the two FTO SNPs and age of onset of obesity. Our results demonstrate a strong association between FTO SNPs rs9939609 (P < 0.043) and rs9930506 (P < 0.029) with BMI in the Italian population. FTO rs9930506 was significantly associated with higher BMI in a G allele dose-dependent manner (BMI + 1.4 kg/m² per G allele). We also observed that the association with BMI of the two FTO variants varied with age, with the carriers of the risk alleles developing an increase in body weight earlier in life. In conclusion, our study further demonstrates a role of the genetic variability in FTO on BMI in a large Italian population.

Objective: Little is known about the prevalence of beta-cell autoantibodies in children with excess body weight. The prevalence of type 1 diabetes autoantibodies and its relation with hyperglycemia was analyzed in 686 overweight/obese children and adolescents., Research Design and Methods: All children underwent an oral glucose tolerance test, and anti-GAD, anti-IA2, and anti-IAA autoantibodies were measured. Autoantibody prevalence was evaluated in 107 normal-weight children for comparison., Results: A single autoantibody was present in 2.18% of overweight/obese subjects and 1.86% normal-weight subjects (P = NS). Postload glycemia was significantly higher in antibody-positive children (133 +/- 69.9 vs. 105.4 +/- 17.7 mg/dl, P < 0.0001) compared with autoantibody-negative subjects. No difference in autoantibody distribution was seen when our cohort was stratified by age, sex, SDS-BMI, pubertal stage, and homeostasis model assessment-insulin resistance (HOMA-IR)., Conclusions: The 2.18% prevalence of type 1 diabetes autoantibodies is similar to that reported in nonobese children. This study provided evidence that excess body weight and insulin resistance do not influence autoantibody frequency.

Background: Very few studies on glucose abnormalities in European overweight/obese children and adolescents are available, and scientific evidence on the value of standard oral glucose tolerance test (OGTT) in childhood is lacking. We therefore aimed to establish prevalence and features of impaired fasting glucose (IFG), impaired glucose tolerance (IGT) and type 2 diabetes (T2D) in a large cohort of Italian overweight/obese children and adolescents and to assess the validity of standard OGTT in the paediatric population., Methods: This is a 1-year observational study conducted on 736 (535 overweight/obese and 201 normal weight) consecutive paediatric patients attending the outpatient clinic of Paediatric Endocrine Unit. Clinical and biochemical parameters were collected for all participants. All overweight/obese subjects underwent OGTT., Results: We observed a high prevalence of IFG (7.66%), more than twice that observed in other European children, but a low prevalence of IGT (3.18%) and T2D (0.18%). IFG was useless to predict IGT, having very low predictive value (7.3%) and sensitivity (17.6%). Compared to normal weight children, overweight/obese subjects showed significant differences in most metabolic and clinical parameters. In the overweight/obese group, having hyperglycaemia was associated to significantly higher blood pressure, homeostasis model assessment for insulin resistance, insulin and triglycerides., Conclusions: In our children, the prevalence of IFG is higher than that reported in other European cohorts, whereas T2D is rare. IFG appears not useful to detect IGT in childhood. Paediatric diagnostic cut-points, glucose load and timing of sampling need to be further validated to define glucose abnormalities in obese children that, compared with normal weight subjects, already are characterised by a different metabolic phenotype.

Background: Childhood obesity has a strong genetic background. The human UBL5 (BEACON) gene has been suggested as a candidate gene for obesity. Previous studies in populations of different ethnicities have shown a significant association between UBL5 variants and measures of body fatness., Aims: To identify mutations that may cause early-onset obesity we screened the UBL5 gene for sequence variations in a cohort of obese children who also had at least one obese parent (BMI >30 kg/m2) diagnosed before the age of 30 years., Methods: We screened the UBL5 gene by PCR-SSCP and sequencing in a cohort (n=30) of obese children (mean age 6.9 +/- 3 yr), and then analysed SNPs by HRMA in a population of 160 obese and 140 lean individuals., Results: Three sequence variations were detected: -422T>C in the 5'-UTR region, and -800T>A (rs10418248) and -860G>T in the promoter region. The SNPs -422 T>C in the 5'-UTR region and -860G>T have never been described before. These two SNPs did not co-segregate with obesity in relatives of the obese carriers. However, since in silico analysis of the -860G>T SNP region predicted a loss of the consensus binding site for RXR-alpha and RXR-beta, both involved in adipose cell regulation, we screened the -860G>T variant in a cohort of 300 individuals, 160 young obese (mean age 33 years) and 140 lean individuals. No differences in genotype distribution or in -860T allele frequencies were found between the two groups (1.8% vs. 1.4%, p = NS). In addition, no association was found between obesity and the previously described -800T>A SNP (rs10418248)., Conclusion: Our data suggest that the UBL5 gene is unlikely to play a major role in the genetic susceptibility to early-onset obesity in our population.

Background: A number of metabolic changes are caused by childhood obesity, including insulin resistance, diabetes, and dyslipidemia. To counteract them, lifestyle modification with changes in dietary habits and physical activity is the primary intervention. Anthropometric parameters may not identify all positive changes associated with lifestyle modifications, whereas circulating adipokines may represent an alternative as biomarkers. The aim of this study was to evaluate adiponectin and leptin levels as markers of positive metabolic outcomes in childhood obesity., Methods: Changes in clinical, anthropometric, and metabolic parameters, including adiponectin and leptin, were assessed in 104 overweight and obese children before and after 1 yr of lifestyle intervention. Obesity and overweight were defined according to the Italian body mass index reference tables for age and sex. Fifty-four normal-weight children were evaluated as controls. Forty-eight of the children (47.5%) returned for follow-up at 1 yr., Results: Compared with normal-weight children, overweight and obese subjects differed significantly at baseline for glycemia, insulinemia, homeostasis model assessment for insulin resistance, adiponectinemia (5.8 vs. 18.2 microg/ml in controls), low-density lipoprotein-cholesterol, and triglycerides. These parameters were all higher in the overweight/obese children. At follow-up, most parameters improved in overweight/obese children. The most significant changes were observed in adiponectin concentration, which increased by 245% (P < 0.0001), reaching the levels observed in normal-weight children. Leptin levels showed changes unrelated to positive metabolic outcomes, remaining high at 1 yr of follow-up in overweight/obese children. Regardless of changes in weight status, children with lifestyle intervention reported changes in homeostasis model assessment for insulin resistance and in adiponectin that were associated with loss of fat mass., Conclusions: After lifestyle intervention, adiponectin increased regardless of changes in weight, whereas no consistent changes was observed in serum leptin. Therefore, circulating adiponectin may represent a good biomarker to evaluate the efficacy of lifestyle intervention in overweight/obese children.

Objective: To test if sequence variations of the SYNTAXIN 1A (STX1A) gene contribute to the susceptibility to type 2 diabetes in a cohort of overweight/obese subjects., Methods: A total of 717 overweight/obese individuals underwent oral glucose tolerance test and were stratified in four groups according to fasting and 2 h glucose levels (NGT, IGT, CGI, T2DM), representing the natural history of diabetes from normal glucose tolerance to overt disease. These subjects were analysed by a two-step genetic study. Functional analysis was performed by electrophoretic mobility shift assay (EMSA) and by supershift with CCAAT/enhancer-binding protein (C/EBP)beta antibody., Results: Among the several sequence variations detected in the STX1A gene, the T allele of the -352 A>T single nucleotide polymorphism in the promoter was found in a lower frequency in the subset of individuals with greater impairment of insulin secretion (CGI). To confirm that a lower frequency of the T allele was associated with this condition, we genotyped a second group of 202 overweight/obese individuals with type 2 diabetes, and the frequency of the T allele was reduced in this group also (P<0.01). Logistic regression confirmed a protective odds ratio (0.49, P<0.01) for the T allele. The EMSA showed that the PRM -352 A allele binds transcription factors with lower affinity compared to the T allele, and incubation with C/EBPbeta antibody 'supershifted' the complex, indicating that C/EBPbeta had a different binding with the PRM -352T allele., Conclusion: A lower frequency of the PRM -352T allele of the STX1A gene was observed in overweight/obese subjects with impaired glucose regulation, particularly among individuals with combined glucose intolerance and overt diabetes. Both these groups have a greater defect in beta-cell function compared to normal and glucose intolerant subjects, and this association together with the functional study suggests a possible role of the PRM -352 A>T variant in insulin secretion.

To evaluate whether a structural defect in the human glucose transporter gene GLUT1 could be involved in the aetiology of insulin resistance, a key factor of non-insulin-dependent diabetes mellitus (NIDDM) and obesity, we performed single-strand conformation polymorphism (SSCP) analysis in 40 subjects (20 NIDDM patients and 20 subjects with familial obesity). The GLUT1 gene, which is involved in basal glucose transport in most tissues, consists of ten exons and encodes a 492 amino acid protein. Population studies have shown a strong association between the X1 allele of an XbaI restriction fragment length polymorphism of the GLUT1 gene and NIDDM. We therefore performed SSCP analysis in NIDDM subjects known to carry at least one X1 allele. Variant SSCP patterns were detected in exons 2, 4, 5 and 9. Sequence analysis of the SSCP variants revealed the presence, in all exons examined, of silent mutations consisting of single-nucleotide substitutions with no amino acid changes. Both NIDDM and obese patients showed a high frequency of polymorphism in the sequence (50% and 35%, respectively). We conclude that the GLUT1 gene is unlikely to play a role in the aetiology of NIDDM and obesity. However, the strong association between the GLUT1 gene and NIDDM, together with the recent family studies showing linkage between chromosome 1p and NIDDM warrant further studies on this chromosomal region.